Section of Dermatology, Department of Internal Medicine, Immunology and Infectious Diseases, University of Bari, Italy.
Contact Dermatitis. 2010 Jun;62(6):343-8. doi: 10.1111/j.1600-0536.2010.01713.x.
Photocontact dermatitis to Ficus carica is induced by furocoumarins present in sap. These substances are generally considered to cause phototoxic reactions.
We conducted a patch test and histopathological study of patients with phytophoto contact dermatitis from the fig tree to evaluate the mechanism underlying the photoreaction.
Patch and photopatch testing with serial dilutions of two natural furocoumarins [5-methoxypsoralen and 8-methoxypsoralen (8-MOP)] contained in plant sap were performed in 47 patients. A synthetic furocoumarin, 4,5',8-trimethylpsoralen, was also tested. Histopathological analyses were made of some positive photoreactions.
Positive photopatch tests reactions to 8-MOP were obtained in 12 of 47 patients, in 4 of them down to a concentration of 0.0001%. Patch tests and photopatch tests to the other two furocoumarins were negative. Histopathological findings on biopsies from positive photopatch tests to 8-MOP showed a dermatitis.
Allergic photoreactions induced by contact with plants containing coumarins are generally regarded as chance findings. This study has demonstrated that phytophoto allergic contact dermatitis resulting from furocoumarins is not an exceptional finding, and should be suspected in subjects with diffuse clinical manifestations in photo-exposed but also non-exposed sites. To differentiate allergic from toxic photoreactions, patch tests need to be performed with serial dilutions of furocoumarins. Histological analysis of a biopsy sample from a positive test site will reveal alterations compatible with a photoallergic contact dermatitis.
桑科榕属植物叶汁中呋喃香豆素可引起光接触性皮炎，这些物质通常被认为会引起光毒性反应。
我们对来自榕属植物的植物-光接触性皮炎患者进行了斑贴试验和组织病理学研究，以评估光反应的机制。
对 47 例患者进行了两种天然呋喃香豆素[5-甲氧基补骨脂素和 8-甲氧基补骨脂素（8-MOP）]的植物叶汁中所含的两种天然呋喃香豆素[5-甲氧基补骨脂素和 8-甲氧基补骨脂素（8-MOP）]的斑贴试验和光斑贴试验，并进行了系列稀释。还测试了一种合成的呋喃香豆素，4,5',8-三甲氧基补骨脂素。对一些阳性光反应进行了组织病理学分析。
47 例患者中有 12 例对 8-MOP 进行了阳性光斑贴试验，其中 4 例在 0.0001%的浓度下呈阳性。对其他两种呋喃香豆素的斑贴试验和光斑贴试验均为阴性。对 8-MOP 阳性光斑贴试验活检的组织病理学检查显示皮炎。
接触含香豆素的植物引起的过敏光反应通常被认为是偶然发现。本研究表明，由于呋喃香豆素引起的植物-光过敏接触性皮炎并非罕见，应怀疑在暴露和非暴露部位有弥漫性临床表现的患者中出现这种情况。为了区分过敏和毒性光反应，需要对呋喃香豆素进行系列稀释的斑贴试验。阳性试验部位活检样本的组织学分析将显示与光接触性皮炎一致的改变。
